Field of the Invention
The present invention relates to a control method for stably performing parallel operation between different types of power generators or between a power generator and a system power supply, and to a control system therefor, and particularly relates to a voltage control method performed in shifting to parallel operation and a voltage control system used in shifting to parallel operation.
Description of Related Art
Generally, in various power supply facilities, power generators that are normally operated and power generators that are operated in an abnormal case or in an emergency case are separately used according to the types of engines or mechanisms thereof, and power generators different in types or characteristics are not operated in parallel. However, in such a case where a part of a device that is normally operated has failed or a peak-cut operation by a standby machine is desired because of great load variation, it is general to perform parallel operation of power generators of the same type including a standby machine, for which adjustment has been performed in advance so that they have the same frequency drooping characteristic and the same voltage drooping characteristic.
Conventionally, while a synchronous power generator is used as a self-sustaining power generator, an induction power generator incapable of independent operation is used only in an operation interconnected with a large system power supply such as commercial power supply.
Upon arbitrary operation interruption of each power generator composing a power supply system, or in a power supply facility of natural energy collecting type whose operation greatly varies depending on time, an ambient environment, or the like, an output voltage drooping characteristic on a power supply side and impedance on a system power supply side always vary depending on combined power supply specifications.